Voltage drop - I think I know, but tell me

[garyk1970]

as Rich said,check for voltage drop before installing new parts,heres how i test...

1)put meter ground on battery post (-).start car(voltage drop will show at any rpm,and running car will keep voltage consistent,so theres no drop from car just sitting there)move positive lead from battery post,battery terminal (very important to see if the actual positive terminal is droping voltage).if those two are IDENTICAL,theres your reference voltage.thoughout this process,go back to this step for reference voltage as battery should/will be charging.
2)now with ref voltage,move positive vom lead to rear of alt charging lug(keep neg where it is for now).should be within 2 tenths or better(perfect would be no drop. .2 or less ok)ie; battery = 13.4, alt =13.6 ok.if not,check connections/terminals/etc closely.if looks good,use one side of jumper cables to verify bad wire buy jumping from alt to battery,retest voltage.

3)grounds. reverse vom meter leads to test all grounds. put positive vom lead on pos battery term post. use neg lead from vom and read battery post,terminal,then go to alt chassis.look for drops.then go to block(not intake,heads,or valve covers,etc....,then go to body,each end of any grounding straps.

 

[Roger]

Do you have a volt booster - could be defective?

 

[Jerryl]

Do you have a volt booster - could be defective?

No VB.
Mixed results reported on them.

 

[Mike70gtx]

Good thread. I'm only getting 54 pounds of fuel pressure when I should be getting over 60 at wot. I'm in process of checking voltage. I have always been low on scanmaster, 12's sometimes high 11's. I did just check voltage on back of alternator and it was 13.6 at idle and if I rev it, it would go to 13.9. Shouldn't it be in the 14's? I'll do some of the other tests suggested here.

 

[TurboDave]

Good thread. I'm only getting 54 pounds of fuel pressure when I should be getting over 60 at wot. I'm in process of checking voltage. I have always been low on scanmaster, 12's sometimes high 11's. I did just check voltage on back of alternator and it was 13.6 at idle and if I rev it, it would go to 13.9. Shouldn't it be in the 14's? I'll do some of the other tests suggested here.

Yes, it should be 14.2

 

[A2000RICH]

Good thread. I'm only getting 54 pounds of fuel pressure when I should be getting over 60 at wot. I'm in process of checking voltage. I have always been low on scanmaster, 12's sometimes high 11's. I did just check voltage on back of alternator and it was 13.6 at idle and if I rev it, it would go to 13.9. Shouldn't it be in the 14's? I'll do some of the other tests suggested here.

depends on the condition of the battery, the number of accesory loads on at a given time and the temperature of the alternator---------output voltage can easily drop as much as a volt from a cold to a hot alternator..............RC